Telephone



Patented Oct. 257 |898. C. S. HEILMAN.

TELEPHONE EXCHANGE SYSTEM.

(Appliaton led Nov. 21, 1898.)

3 Sheets-Sheet l.

No. 6I3,036.

(No Medel.)

No. 6|3,036. Patented Oct-25,1898.

c. s.. HEILMAN. '.TELEPHNE EXCHANGE SYSTEM.

(Application "filed Nov. '21, 1896.)

(No Model.) 3 Sheets-Shet 2.

W.. E.. .mm

No. 613,036. Patented oct. 25, |398.

c. s. HEILMAN.

TELEPHONE EXCHANGE SYSTEM.

(Application filed Nov. 21, 1898.)

(No Model.) 3 .SheetsfSheet 3.

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UNITED STATES PATENT OFFICE.

CHARLES S. HEILMAN, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR, BY DIRECT AND MESNE ASSIGNMENTS, OF THREE-FOURTHS TO 'JAMES S. THOMPSON, OF NORTI-ITONAWANDA, NEW YORK. Y 'V TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 613,036, dated October 25, 1898.

, Application tiled November 21,1896. Serial No. 612,946. (No model.)

To @ZZ whom, it may concern..-

This invention relates to a telephone sysro tem, and has the object to improve the construction of the annunciator, the couplingplug, the means for returning the couplingplug to its normal position, to prevent looping in the talking-circuit when the subscriber of one board is connected with a subscriber on another board, and to improve the system in other respects.

In the accompanying drawings, consisting of three sheets,Figure 1 is afragmentary longizo tudinal sectional elevation ofthe switchboard,

showing one of the subscribers lines and connecting parts in their normal position. Figs. 2 and 3 are horizontal sections in lines 2 2 and 3 3, Fig. l, respectively. Fig. e is a front end view of one of the subscribers couplingplugs. Fig. 5 is a sectional elevation similar to Fig. l, showing the position of theparts when the subscriber calls up the central office. Fig. 6 is a vertical transverse section in line 3o 6 6, Fig. l. Fig. 7 is a similar section in line l 7 7, Fig. 5, showing the key shifted for switching in the operators talking apparatus. Fig. S is a perspective view of one of the switchplungers and the plug-releasing link. Fig. 9 3 5 is a sectional View, on a reduced scale, showing the position ofthe parts when Vthe lines of two subscribers are coupled. Fig. l0 is a front elevation, on a reduced scale, showing the means whereby the subscribers on one 4o operators or terminal board may be coni ofthe front board, and each frame consists, Be it known that I, CHARLES S. I-IEILMAN-,a citizen of the United States, residing at Phila" essentially, of a base Z), which is fastened to the top of the shelf, two uprights or standards b', arranged lengthwise on opposite sides of the rear portion of the base, a lip h2 de- 55 pending from the rear end of the base and secured to an angle-plate b3 on the rear edge of the shelf bya screw b4, and a cross-bar b5, connecting the upper rear portions of the standards.

C represents the electromagnet, having its coils arranged one above the other and secured with their rear ends to the cross-bar b5 of the frame.

c is the armature, which is arranged vertically in front of the poles of the electromagnet end, which is pivoted with its lower portion on a horizontal pin c2, connecting the standards.

Between the base ofthe annunciator-frame: 7o and the electromagnet a longitudinally-movable plunger is arranged, which consists, eslsentially, of a bottom plate cl, having a ,wideL .-j rear portion and a narrow front portion, and... two flanges d', arranged lengthwise on oppo- 75 site sides ofthe wide and narrow portions of the base. The bottom of the plunger slides on top of the base of the annunciator-frame and the flanges on its rear portion bear against the inner side of the standards, as represented 8o in Figs. l, 2, 5, 6, and 7. The forward movement of the plunger is effected by springs d2, arranged lengthwise over the side portions of the plunger and secured with their rear ends to the rear end of the plunger and with their front ends to the standards. The plunger is held down on the base of the annunciatorframe by rollers d3, pivoted onthe inner side of the standards and bearing upon the rear portions of the iianges of the plunger, as rep- 9o resented in Figs. 1, 2, and.

E represents a locking-lever whereby the plunger is held in its retracted position and which is arranged lengthwise above the rear portion of the plunger. This locking-lever is pivoted with its rear end by a transverse pivot e to the standards, so as to swing vertically with its front end, and its under side is provided near its pivot with a notch, forming front and rear shoulders c' e2, respectively. :oo

This notch is adapted to engage with a lugl e3, arranged on the rear portion of the bottom of the plunger when the latter is retracted and the locking-lever is depressed, thereby holding the plunger in its retracted position against the forward pull of the springs d2. The downward movement of the front portion of the locking-lever is limited by means of a stop lug or teat e4, which is formed on the under side of the locking-lever and which bears against the plunger-bottom when the locking-lever is in its operative position. Thislugis preferably V-shaped, so that it can penetrate any dust or clear away any other slight obstruction on the plunger, thereby enabling the locking-lever to always descend into its lowermost or operative position.

F represents an intermediate or releasing lever whereby the locking-lever is held in its depressed position when the plunger is retracted and which is pivoted on the same pin c2 on which the armature is pivoted. The releasinglever is arranged vertically, with its y connectedin front of the armature by a crossy bar f2.

f3 is a forwardly-projecting lug formed on the front side of the armature and provided with a notch f4, which receives the cross-bar 3 5 f2 of the releasing-lever.

p is removed from said cross-bar.

During the last portion of the inward or rearward movement of the plunger the rear i side of its locking-lug engages with the rear side of the notch. in the locking-lever, and thereby aids gravity in producing a quick downward movement of the locking-lever. The instant the latter reaches its lowermost position the lower end of the releasing-lever is swung rearwardly over the free end of the locking-lever,whereby the latter is prevented from rising by the forward pressure of the locking-lug of the plunger against the front side of the notch in the locking-lever. The backward or locking movement of the lower arm of the releasing-lever is produced by the forwardly-overhanging weight of the upper arms thereof. When the armature is attracted by the electromagnet, its hook, which embraces the cross-bar of the releasinglever, pulls the upper arms of the latter backwardly and its lower arm forwardly until it clears the locking-lever, whereby the latter is raised and the plunger is projected forwardly or outwardly by the springs d2. The notch in the lug of the armature is of such length so as to produce a loose fit and permit of some play between the armature and the releasing-lever. When the armature is retracted, it rests by gravity with the rear side of the notch in its-lug fs against the cross-bar of the releasing-lever, while the front side of said notch When the armature is attracted, it moves idly toward the electromagnet until the front side of the notch in the armature-lug strikes the crossbar of the releasing-lever, after which the upper end of the latter is moved backwardly with the armature and its lower end is moved forwardly out of engagement-with the locking-lever, thereby releasing the latter and the plunger. By allowing the armature to move independent of the releasing-lever during the first portion of its movement toward the electromagnet the armature acquires a momentum and strikes the releasing-lever with a blow of considerable force, thereby insuring the release of the locking-lever and permitting a comparatively light or low wound electromagnet to be employed. The throw of the releasing and locking levers is regulated by a horizontal adjusting-screw g, arranged lengthwise between the standards and engaging with its inner screw-threaded portion in an internally-screw-threaded eye g on the inner side of one of the standards and supported loosely with its outer portion in an eye g2 on the same standard. The inner end of the adjusting-screw bears against a projection on the lower arm of the releasing-lever, and its outer end is provided beyond the annunciator-frame with a thumb-piece for turning the same conveniently.

H represents a switch or key lever whereby the various circuit changes in the subscribers line are effected during the operation of connecting one subscriber with another and which also serves as a visual signal to the operator when a subscriber calls up the central office. This key-lever extends horizontally through an opening h in the front board and is provided at its outer end with a knob or handle h', having the form of a cube, which bears the number of the respective subscriber. The inner portion of the key-lever is arranged between the front portions of the iianges of the plunger and is pivoted thereto near its middle by a horizontal pin h2, which connects these anges. The inner arm of the key-lever is provided with two lugs h3 h4, projecting laterally in. opposite directions and forming a cross-head, and this lever is normally held in a horizontal position by making the inner arm thereof somewhat heavier than the outer arm, although the same effect can be produced by the aid of springs.

it" represent upper and lower insulated contaets which are connected by a Wire 'i2 with one end of the coils of the electromagnet and which are supported on a cross-bar i3, connecting the lower front portions of the standards. The lower contact z" is adapted to bear against the under side of the lng h3 on one side of the key-lever and the upper contact overhangs the lug h4 on the opposite side of the key-lever when the latter is in its retracted position.

j isa lower insulated coupling-contact arranged lengthwise over the key-lever and connected by wire j' with the opposite end of IIO VIIS

the coils of the electromagnet. This contact is secured with its rear end to a cross-bar jz,

which' connects the upper front portions of,

the standards, while its front end rests on the bottom of a coupling socket or openingjs, which is formed in the front board above the key-lever opening h.

j 4 is an upper insulated coupling-contact arranged in the upper portion of the coupling-socket and adapted to bear upon the lower contactj by gravity. This upper contact is pivoted with its upper end to a bracket jf, which is secured to the rear side of the front board and inclines from its upper end rearwardly to its lower free end. j

7s 71: are two contacts `secured to opposite sides of an opening 7.52, which is formed in a `rear supporting-board K, arranged vertically in rear of` the front board, and K is a movable contact-plug adapted to bear against the front sides of both contacts and establish electrical communication between the same when the contact-plug `is fully retracted.

7a3 is a wire leading from the contact 7c to the bracket j5, supporting the coupling-contact jt, and K4 is a wire leading from the other contact 70 to a binding-post 705 on the cross connectingboard at the central cinec, to which post one side of the subseribers apparatus L is connected by a wire 7o". The opposite side of the subscribers Aapparatus is connected by a wire Z with another bindingpost Z on the cross connecting-board, and

this post is connected by a wire Z? with the angle-plate b3 on the supporting-shelf. The metallic frame connected with the angle-plate b3, the plunger resting on the frame, and the key-lever pivoted on the plunger form parts of the electrical conductor in dierent positions of these parts. When the parts are in the normal position, (shown in Figs. l, 2, and 6,) the subscribers signaling or calling circuit is established from one side ofhis apparatus L, through wire Z, binding-post Z', wire Z2, angle-plate b3, annunciator-frame, plunger, keylever, contact t, wire 2, coils C, wire j', lower coupling-contactj, upper coupling-contactj4, bracket j5, wire 7c3, contact lo, plug K', contact 7c', wire 7a4, binding-post 765, and wire k6 back to the opposite side of the subscribers apparatus. Upon `calling up the central ofiice in this condition of the line the electromagnet is energized, the armature is attracted, and the plunger is released, thereby permitting the springs to project the plunger into the position shown in Fig. 5, whereby the subscribers circuit is broken by the lug h3 of the key-lever leaving the contact 7l.

In projecting the plunger and key-lever to their outer position the operators night-bell or signal M is looped in by the following mechanism: i

m represents a movable upper contact which is arranged lengthwise on one side of the plunger and secured with its rear end to the supporting-shelf, while itsfront end overhangs a lower stationary contact m', secured to the shelf. One end of the bell-coils is connected by a wire m2 with the upper contact m,while the other end of the coils is connected by wire m3 with one pole of an electric generator 'm4, the opposite pole of which is connected by wire m5 with the lower contact m.

fm( is an upwardly-projecting arm formed on the movable contact m in front of the lug h3 of the key-lever. During the last portion of the forward movement of the key-lever with the plunger an insulating-block 'm7 on the front side of the lug h3 of the key-lever bears against the arm 'm6, whereby the upper movable contact is depressed into engagement with the lower contact m', as represented in Fig. 5, and the circuit for ringing the night-bell is established through the wire m3 leaving one side of the bell M, generator m4, wire m5, lower contact m', upper contact fm, and wire 'm2 back to opposite side of the bell.

The mechanism and circuits which enable the operator to signal or call up a subscriber are constructed and arranged as follows:

N represents an electric generator having one of its poles connected bya wire n with a contact n', which is secured with one end to the rear side of the front board and is arranged with its free end over the lug h3 of the key-lever when the latter is retracted with the plunger. The opposite pole of the generator N is connected by a wire n2 with a contact n3, which is secured with one end to the rear side of the frontV board and is arranged with its free end over an insulatingblock 'n4 on the lng h4 of the key-lever when the latter is retracted. Upon depressing the outer or front arm of the key-lever when the latter is retracted, as shown by dotted lines, Fig. l, the lug h3 on the inner arm thereof is lifted out of engagement with the contact t" and into engagement with the contact fn', while the insulating-block n* on the opposite key-lever lug 77,4 lifts the contact n3 into engagement with the contact t', whereby the circuit for calling up the subscriber is established through wire n from one pole` of operators generator N, contact '11,', lug h3, keylever, frame, angle-plate b3, wire Z2, bindingpost Z', wire Z, subscribers apparatus L, wire k6, binding-post h5, wire 7a4, contact 7s', plug K', contact k, wire k3, bracket j5, contact j, contact j, wire j, coils C, wire t2, contact t', contact n3, and wire 'n.2 bac-k to the opposite pole of the operators generator N.

The operators listening and l speaking apparatus is looped into the subscribers line by the following means:

O represents the operators listening-telephone, and o a wire leading from one side of this telephone to the contact/m.

o2 is a rock-lever pivoted on the rear side of the front board so as to swing in a vertical tends rearwardly over the key-lever, while its upper arm stands in rear of the bracket IOO IIO

3'5, which supports the upper coupling-con- 01 is a rearwardly-projecting nger formed on the upper end of the arm m6 on the contact m and adapted to overhang the lug h3 of the key-lever when the latter is in its projected position. Upon depressing the outer arm of the key-lever when the latter is in its projected position, as represented in dotted lines, Fig. 5, the lug h3 of the key-lever engages against the under side of the finger o4 and lifts the upper contact m from the lower contact m', thereby opening the night-bell circuit at this point, and at the same time the insulating-block n4 on the lug h4 of the key-lever engages against the under side of the lower arm of the rock-lever o2 and turns the same until its upper arm bears against the bracket j5, whereby the talking-circuit between the operators telephone 0 and the subscribers telephone is established through wire o', leading from one side of the operators telephone, contact m, arm m6, finger o4, lug h3, key-lever, plunger, angle-plate b3, wire Z2, bindingpost Z, wire Z, subscribers telephone apparatus L, wire k6, bindingpost Z55, wire h4, contact 7o', plug K', contact k, wire 7c3, bracket j5, rock-lever 02, and wire oS back to the opposite side of the operators telephone. While the inner arm of the key.- lever is raised for looping in the operators telephone, the finger o4, which is arranged under the contact n', is prevented from touching the latter by an insulating-block 05, secured to the under side of the Contact n', thereby preventing the generator N from being looped into the main line during the operation of looping in the operators telephone.

It will be observed that when the operator talks to a subscriber the talking-circuit does not include the annunciator-coils of the respective subscriber.

P, Figs. l, 4, and 9, represents the coupling-plug, whereby one subscriber is coupled with another and which is seated, when not in use, in a socket P', formed in the front board of the switch adjacent to the terminal of the respective subscriber. The body of the plug consists of vulcanite or other insulating material, and its front portion p is smaller than its rear portion p, so as to form a shoulder p2 on the body.

I 193294 are two terminals,which extend lengthwise through the rear portion of the plugbody and along opposite sides of the front portion of the body.

p5 is a casing which incloses the rear por- -tion of the body of the plug and which is adapted to abut against a stop or board p6, arranged in rear of the front board, for limiting the inward movement of the plug into its normal or home socket.

q q' represent two conducting-wires, which connect the terminals P3194, respectively, with the subscribers binding-posts 755 Z on the cross connecting-board. A portion of these plugwires q q' are arranged in a cord Q, which eX- cured, thereby forming a loop or bight, which is paid out when the plug is withdrawn from its socket in making connection with another subscriber. The take-up pulley q2 is mounted in a pulley-frame g3, which is constantly pulled backwardly by any suitable contrivance, so as to take up the slack in the cord and pull the plug back into its normal socket when the plug is uncoupled from another subscriber. The preferred means for accomplishing this result consists of a cord r, secured at one end to the pulley-frame and wound with its opposite end around a spring-drum R, which is mounted on a supporting-board r', arranged in rear of the supporting -board K. Upon withdrawing the plug-cord the drum-cord in unwinding from the drum strains its spring until the pulley strikes the rear side of the stop-board, when the further outward movement of the cord and the unwinding movement ot' the drum are arrested, thereby preventing undue straining of the spring.

ln order to divert the circuit from the annunciator-coils and connecting parts to the terminals of the coupling-plug upon withdrawing the latter the main-line circuit is opened or broken beyond the coils by removing the plug K from the contacts Zo 7d, thereby cutting out the coils when the coupling-plug is withdrawn. For the purpose of accomplishing this automatically by the withdrawal of the coupling-plug the contact-plug K is connected with or formed integrally with the frame of the take-up pulley, whereby the first portion of the outward movement the coupling-plug removes the plug K from the contacts Zak and opens the main line. lf desired', the wires k3 104 may be connected with contacts k7 las, arranged on the front side of the stop-board, as shown in vdotted lines, Fig. l, in which case the metallic case p5 of the coupling-plug can be utilized as a means for bridging the contacts k7 708 for restoring the line to its normal condition.

Upon withdrawing the coupling-plug of one subscriber and inserting the same into the coupling-socket ,7'3 of another subscriber the contacts jj1 in the coupling-socket are separated and the terminals of ythe coupling-plug are engaged, respectively, with the couplingcontacts jj, and when the plungers and keylevers of the subscribers so connected are retracted into their normal position the talkingcircuit between these subscribers is established as follows and as shown in Fig. 9, in which subscribers Nos. 25 and 74 are connected: Beginning on one side of the subscribers apparatus No. 25, the current passes through wireZ bindinfrost Z wire Z2 angle- 3 C p 7 3 b plate b3, annunciator-frame, key-lever and its lug h3, contact t', wire z2, coils C, wire J', lower couplingcontact j, terminal contact p3 of IOO IIO

ISO

coupling-plug, wire q, binding-postfkfs, wire k6, subscribers apparatus No. 74, wire Z, binding-post l', wire q,plugte1minal p4, upper coupling-contact j, bracket j5, wire 7c3, contact 7a, plug K', contact 7o', wire 7a4, bindingpost ks, and wire 7i;6 back to the opposite side of subscribers apparatus No. 25.

The coupling-plug is inserted into the coupling-socket ,7'3 until its shoulder p2 engages with the front board or the escutcheon a', surrounding the outer end of the socket, and the plug is confined in said socket by the following mechanism, so that it cannot be withdrawn without operating the generator of either subscriber or that of the operator:

S represents a stem projecting forwardly from the front end of the plug-body and provided with a coupling-head s, having a conical or inclined front side and an abrupt rear y side.

T represents a vertically-movable lockingpawl whereby the coupling-plug is confined in the coupling-socket and which is pivoted with its rear end to the upperends of the standards b'. The front end of the pawl is provided with a hook t, which is normally arranged in the path of the coupling-head and which has a beveled front side and an abrupt rear side. Upon inserting the coupling-plug in the coupling-socket js the conical front side of the coupling-head engages with the beveled front side of the hook on the couplingpawl, whereby the latter is lifted out of the path of the head, and after the head has passed the pawl-hook the latter drops, so as to stand in rear of the coupling-head, thereby preventing the coupling plug from being withdrawn unless the locking-pawl is raised.

Urepresents a lifting rod or link which connects the plunger with the locking-pawl and whereby the latter is lifted for releasing the coupling-plug when the plunger is projected. This link is provided at its upper end with a Vertical slot u, through which the lockingpawl passes, and the latter is provided on opposite sides of the link with pins or stops u',

which prevent the link from being displaced on the locking-pawl. The lower end of the link is bifurcated or divided into two arms u2, which straddle the plunger and rest on the base of the annunciator-frame, and the locking-pawl rests on the lower end of the slot in the upper end of the link. Each of the link-arms is provided with a transverse slot us, which extends in the longitudinal direction of the plunger and which receives a pin n4, secured to the plunger.` In the retracted position of the plunger its pins ui engage with the rear ends of the slots in the lower arms of the link and the latter is shifted rearwardly at such an angle as to permit the locking-pawl to descend and stand with its hook in the path of the vhead on the couplingplug, as represented in Fig. 1. During the first portion of the outward movement of the plunger it moves idly without affecting the link; butduring the last portion of its out- The object in slotting the lower end of the link is to secure a certain amount of dead forward movement of the plunger before the locking-pawl is alfected, thereby avoiding an excessive movement of the latter, which otherwise would take place if the lowerend of the y,

link were pivoted to the plunger. 'Upon inserting the coupling-plug into the couplingsocket when the plunger is retracted the head of the coupling-plug while engaging with the locking-pawl moves the latter upwardly in the upper slot of the link without affecting the latter. i

The operation of my improved telephone system is as follows: Vhen the subscriber calls up the central office, the plunger is released and projected together with the keylever, whereby the `main line is opened between the contact z" and lug h3 of the keylever and the subscribers bell stops ringing, thereby indicating to the subscriber that his call has been received at the central office. At the same time the projected key-lever or the sounding of the night-bell, the circuit of which has been closed, serves as a signal to the operator. The operator now loops his listening-telephone into the main line by depressing the outer end of the key-lever while the latter is in its projected position and ascertains with which subscriber the calling subscriber wishes to communicate, when the operator pushes the key-lever inwardly` to its normal locked position, thereby cutting out his listening-telephone. The operator next depresses the outer end of the key-lever of the called subscriber while the lever is retracted, thereby looping in the operators generator N and ringing' up the called subscriber. In thus signaling the called subscriber the plunger and key-lever are not projected when released by the electromagnet, because the operator retains hold of the key-lever until the generator has been cut ont again. Having called up the desired subscriber, the coupling-plug of the calling subscriber is pulled out of its socket and inserted in the couplingsocket of the called subscriber, thereby establishing the talking-circuit between the two subscribers. If desired, the talking-circuit can be produced by inserting the couplingplug of the called subscriber into the coupling-socket of the calling subscriber. Then the talking-circuit is established between two subscribers, the particular subscriber whose coupling-plug has been withdrawn has his coils cut out by opening the line between the contacts k 7c' in the act of withdrawing his coupling-plug, so that conversation is carried IOO IIO

j' count of the reduction in resistance.

on through only one set of coils, whereby thev efficiency of the service is increased on ac- As the coupling-plug of one subscriber is locked in the coupling-socket of the other subscriber the operator cannot project the key-lever into the position where he can loop in his listenin g-telephone without first looping in his generator. It is therefore impossible for the operator to attempt to listen to the conversation of the subscribers without being detected. When the subscribers have nished talking and either one of them rings off,the coils of the subscriber which are in circuit are energized, whereby the respective plunger and key-lever are released and projected, indicating to the operator that the conversation has terminated. The operator now pulls out the coup- I turns the coupling-plug of the calling subscriber to its respective socket, whereby the ringing-circuits are again restored to their normal condition ready for another call.

If the subscribers fail to ring O, the operator can release the locked coupling-plug by depressing the outer end of the respective key-lever when the latter is retracted, thereby looping in the operators generator and projecting the key-lever, together with the plunger, after which the parts can be restored to their normal position, as before described.

For the purpose of enabling the subscribers on one of the operators boards to be connected with the subscribers on the board of another operator without the possibility of any operator looping in on the circuit without detection the following means are-provided:

V lV V2 represent three switchboards upon which the annunciators or terminals and the coupling-plugs of three groups of subscribers are respectively arranged.

'u u' 'U2 represent a number of terminals or annunciators which are arranged adjacent to each switchboard and each of which is constructed substantially the same as the annunciator heretofore described,and shown in Figs. l, 2, 6, and 7. Each annunciator of one board is connected by individual wires w fw with an annunciator on one of the other v boards, the two annunciators so connected forming a pair which are exclusively con? nected with the ends of the respective wires w w', no provision being made for looping into these Wires at a point intermediate of the pair of annunciators. The wires tu w of each pair are connected at their ends with the brackets j, which carry the upper couplingcontactsj4, and with the metallic supportingframes of both annunciators of each pair.

As represented in Fig. 10, each of the switchboards is connected with every other switchboard by two pairs of annunciators, the number being determined by the demand. Assuming that subscriber No. 24 on board V wishes to be connected with subscriber No. 78 on board V2, the connection between the same would be made, as shown in Fig. l0, in the following manner: Having ascertained from the calling subscriber No. 24 in the manner heretofore described with which subscriber he wishes to communicate, the operator depresses the key-lever of one of the annunciators o and loops in his generator in the circuit which includes this annunciator and the companion annunciator v2 on switch V2, whereby the plunger and the key-lever of the last-mentioned annunciator are projected and the operator of board V2 is notied that a subscriber on his board is Wanted. The operator of board V immediately upon calling up operator of board V2 pulls out the coupling-plug belonging to subscriber No. 24: and inserts it into the coupling-socket of the annu nciator ein circuit with the annunciator v2, which has just been rung up. The operator of board V2 now loops in his listeningtelephone and asks the calling subscriber with which subscriber he wishes to be connected, and having ascertained that he Wants No. 78 he rings up the called subscriber No. 78, then pulls out the latters coupling-plug and inserts the same into the coupling-socket of the rung-up annunciator v2, whereby the subscribers Nos. 24 and 78 are placed in communication with each other. If desired, the operator of board V can loop his listening-telephone into annunciator o and himself inform operator of board V2 that subscriber No. 24 Wishes to speak to subscriber No. 78, which would avoid the necessity of asking subscriber No2-t twice with whom he wishes to communicate. When a subscriber rings off, the annunciator having the highest resistance will be operated and project its plunger and key-lever, thereby signaling the respective operator to disconnect the lines. Assuming that operator of board Vhas been so signaled, he pulls the coupling-plug out of the socket of annunciator fu and returns the plug to its normal position and at the same time loops in his generator in the circuit, which includes this pair of annunciators, so that the plunger and keylever of the companion annunciator u2 on board V2 will be projected and signal the operator of board V2, in response to which the latter pulls the coupling-plug of subscriber No. 78 out of theannunciator-socket @2 and returns it to its normal position. Inasmuch as it is necessary for the operator who first receives the ring-olf signal from the subscribers to signal the operator of the other board to the same effect, more work devolves upon the Iirstmentioned operator, and for the purpose of equalizing this Work when each board is connected by a number of anuunciatorcircuits with every other board one-half of the coils of the annunciators of each board are wound with a high resistance and the other one-half with a low resistance, so that the work devolving upon each operator by reason of receiving IOO IIO

the rst ring-off signal is approximately uniformly divided. In order to enable the operators to distinguish whether the ring-off is the primary signal from the subscribers or the secondary signal from another operator, the high and low resistance annunciators are distinguished in some Way. For instance, the escutcheon or key-lever knob of the high-resistance annunciators may be colored red and those of the low-resistance annunciators ily determine Whether the ring-off is the primary signal of the subscribers, which demands a restoration of the plug to its normal position and a ring-olf to the other operator as a secondary signal to also restore his plug to the normal position, or Whether the ringo is the secondary signal from the other operator and only requires the restoration of the plug to its normal position.

I claim as my inventionl. The combination with the electromagnet and its armature, of a horizontally-movable switch-plunger provided with a shoulder, a horizontal locking lever provided with a shoulder adapted to engage with the shoulder of the plunger for holding the latter in its re tracted position, an upright releasing-lever adapted to engage its lower arm with the locking-lever for holding the latter in its operative position, and means whereby the plungeris projected when released by the lockinglever, substantially as set forth.

2. The combination with the electromagnet and its armature,of a switch-plunger provided with a shoulder, alocking-lever controlled by said armature and provided With a shoulder Which is adapted to engage With the shoulder of the plunger, and a Wedge-shaped teat or projection arranged on the locking-lever and adapted to rest on the'plunger and limit the locking movement of said lever, substantially as set forth.

3. The combination with the electromagnet and its armature, of a horizontally-movable switch-plunger provided with a shoulder, a horizontal locking lever provided with a shoulder adapted to engage with the shoulder of the plunger for holding the latter in its retracted position, an upright releasing-lever adapted to engage its lower arm With the locking-lever for holding the latter in its operative position and having its upper arm loosely connected with the armature, and means whereby the plunger is projected when released by the locking-lever, substantially as set forth.

4f. The combination with the electromagnet having an armature, of a switch-plunger provided With a shoulder, a locking-lever provided with a shoulder adapted to engage with the shoulder of the plunger for holding the latter in its retracted position, a releasinglever pivoted concentric With the armature, loosely connected with the armature and adapted to hold the locking-leverin its operative position, and means whereby the plun- .With a shoulder, a horizontal locking-lever pivoted with its rear end on said frame and provided with a shoulder adapted to engage with the shoulder of the plunger for holding y the latter in its retracted position, an upright releasing-lever pivoted on the supportingframe and adapted to engage its lower arm with the front end of the locking-lever for holding the latter in its operative position, across-bar arranged on the upper arm of the releasing-lever, a lug arranged on said armature and provided with a notch which receives the cross-bar of the releasing-lever, and means whereby the plunger is projected when released by the 1ocking-lever,substan tially as set forth.

6. The combination With the supportingframe and the electromagnet provided with an armature, of a horizontallymovable switchplunger guided in said frame and provided With a shoulder, a horizontal locking-lever pivoted with its rear end on said frame and provided with a shoulder adapted to engage with the shoulder of the plunger for holding the latter in its retracted position, a releasing-lever pivoted on the front portion of the supportingframe and having its upper arm connected with the armature While its lower arm is adapted to control the locking-lever, and an adjusting-screw mounted on the supporting-frame and having its frontend bearing against the releasing-lever While its rear end is arranged adjacent to the rear end of the supporting-frame, substantially as set forth. l

7. The combination with an electromagnet, of a switch-plunger controlled by said electromagnet, a key-lever fulcrumed on `said plunger and carried bodily back and forth With the plunger, and a circuit which may be openedand closed by turning the key-lever on its fulcrum, substantially as set forth.

8. The combination With the main-line circuit and the electromagnet arranged in said circuit, of a switch-plunger, controlledby the electromagnet, a key-leverfulcrumed on the plunger and carried bodily back and forth with the plunger, and a break which is arranged in the 1nain -line circuit and which is opened and closed by the back-and-forth movement of the key-lever, substantially as set forth.

9. The combination with the electromagnet havinga terminal contact, of a switch-plunger IOO IIO

.- carried back and forth With said plunger and adapted to out the generator-circuit into or out of the main line, substantially as set forth.

l1. The combination With the electromagnet and the switch-plunger controlled by the electromagnet, of a local signal-circuit and a key-lever fulcrumed on the plunger so as to be carried bodily back and forth with the plunger and adapted to open and close the local signal-circuit, substantially as set forth.

12. The combination With the electromagnet and the switch-plunger controlled by the electromagnet, of a local signal-circuit, acontact arranged in the signal-circuit and provided With an arm, and a key-leverfulcruined on said plunger so as to be carried bodily back and forth With said plunger and provided With a lug adapted to engage With said arm and close the signal-circuit, substantially as set forth.

13. The combination with the electromagnet and the switch-plunger controlled by the electromagnet, of a speaking-circuit, and a key-lever adapted to open and close the speaking-circuit and fulcrumed on the plunger so as'to be carried bodily back and forth with the plunger, substantially as set forth.

14. The combination With the electromagnet and the switch-plunger controlled by the electromagnet, of a speaking-circuit, a rocklever adapted to open and close the speakingcircuit and a key-lever pivoted on the plunger and adapted to operate the rock-lever, substantially as set forth.

15. The combination with the electromagnet and the switch-plunger controlled by the electromagnet, of a contact arranged in a signal-circuit and in a speaking-circuit and provided With an arm having a finger, a rocklever adapted to open and close the speakingcircuit, and a key-lever pivoted on the plunger and adapted to bear against said arm for closing the signal-circuit or against said finger and rock-lever for closing the speaking-circuit, substantially as set forth.

16. The combination With the electromagnet provided with an upper generator contact and a lower main-line contact on one of its terminals, a generator-circuit having a contact arranged adjacent to said upper contact, a contact arranged in both a signal-circuit and a speaking-circuit, and a key-lever pivoted on the plunger and adapted when in its retracted position to open and close the main-line and the generator circuits and when in its projected position to open and close the speaking and signaling circuits, substantially as set forth.

17. The combination With the electromagnet and the coupling-plug,of a switch-plunger controlled by the electromagnet, and a locking-pawl adapted to hold the coupling-plug in its coupled position and controlled by the plunger, substantially as set forth.

18. The combination with the elect-romagnet and the coupling-plug provided with a shoulder, of a switch-plunger controlled by the electromagn et, and a pawl connected with said plunger and provided With a hook adapted to engage with the shoulder of the coupling-plug, substantially as set forth.

19. The combination with the electromagnet and the coupling-plug, of a switch-plunger controlled by the electromagnet, a lockingpawl adapted to hold the coupling-plug in its coupled position, and a link connecting the switch-plunger and locking-pawl, substantially as set forth.

20. The combination with the electromagnet and the couplin g-plu g, of asWitch-plun ger controlled by the electromagnet, a lockingpaWl adapted to hold the coupling-plug in its coupled position, and a link connected at one end with the switch-plunger and connected loosely at its opposite end with the lockingpawl, substantially as set forth.

21. The combination With the electromagnet and the coupling-plug, of a switch-plunger controlled by the electromagnet, a lockingpawl adapted to hold the coupling-plug in its coupled position, and a link connected at one end With the locking-pawl and loosely connected at its opposite end with the switchplunger, substantially as set forth.

22. The combination with the electromagnet and the coupling-plug, of a switch-plunger controlled by the electromagnet, a lockingpaWl adapted to hold the coupling-plugin its coupled position, and a link provided at one end with a slot through Which the lockingpawl passes and at its opposite end with a slotwhich receivesaprojection on the switchplunger, substantially as set forth.

23. The combination With the non-conducting body of the plug havinga contracted front portion, of two conducting-terminals extending through the rear portion of the body and along opposite sides of the front portion of the body, and a head arranged on the front end of the body and provided With an inclined front side and an abrupt rear side which is adapted to be engaged by alocking-pawl, substantially as set forth.

24. The combination With the mainline, of a signal mechanism arranged in a branch of the main line, a movable coupling-plug arranged in another branch of the main line, and a switch which is arranged in the signalmechanism branch but which is not electrically connected with said plug, said switch being operated to open the signal-mechanism branch upon withdrawing the plug and to close the signal-mechanism branch upon returning the plug, substantially as set forth.

Witness my hand this 7th day of November, 1896.

CHARLES S. HEILMAN.

Witnesses:

JNO. J. BoNNER, KATHRYN ELMORE.

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